Here are the Frequencies Matt, Hope this helps.
ORD CLEARENCE 121.60
ORD GROUND= 121.76, 121.75, 121.90
ORD TOWER(SOUTH 120.75)(NORTH=126.90)
ORD DEPARTURE= 125.0, 125.40, 127.40
ORD APPROACH= 119.0, 125.7, 128.45
Also what new scanner are you getting? I am getting a PRO-29 60 Channel.
Tower : deals with arriving and departing aircraft on/off the runways, and planes within about a 5-10 mile radius of the field (airplanes doing patterns, arriving aircraft ready for landing, departing aircraft until about 1 min after takeoff).
Ground : Deals with taxiing planes from the aprons/terminals to the respective departure runway. Also taxies planes after they have just arrived on the runway, cleared the runway, and need taxi instrus to their apron or terminal.
Apron : Often at busy airports, airlines have to call up for pushback clearance out of the gate. They may give taxi instructions from the gate to the taxiways before ground takes over.
Anyway, this should really be discussed in a different thread.